Any intervention into human vasculature can give rise to the need for capturing and retrieving debris, such as grumous matter, emboli, or thrombi, from the affected vessel. Filters of various types have found use, for example, in trapping blood clots and other debris released into the bloodstream. Many filters, however, can be only partially effective in capturing the debris from surgical or catheterization interventions because deployment of the filter within the blood vessel may not provide complete filtration. That is, a filter may not effect filtration across the full cross-section of the blood flow through the vessel. This may result from failing to maintain an optimum fit of the filter within the vessel wall. Where a filter basket is used, another cause for concern is that the basket may not always be fully opened upon deployment within the vessel.
Specifically, filters are traps that have been designed to be used to collect dislodged matter, such as grumous matter, emboli or thrombi, during procedures such as stent installation in coronary saphenous vein grafts. Such filters or traps serve to provide protection from distal embolization that might result in a major adverse coronary event or other acute complication. Embolization of debris which might be released during such procedures and the resulting sequellae have been described in reports documenting major adverse cardiac event rates. Such events include acute myocardial infarction, revascularization and even death.
In order to address such acute embolic-related complications, distal filtration and protection devices have been developed. Such devices have been designed to work with existing interventional modalities. Such devices provide debris-filtering protection during invasive procedures and are intended to prevent complications of particulate embolization.
Such distal filtration and protection devices are typically deployed at a location along a vessel of the body at a desired location. Such deployment is performed by extending the device outwardly from the distal end of a catheter. In order to facilitate deployment, the device to be deployed typically has components made from a shape-memory or highly elastic material. Consequently, they are able to be collapsed within the catheter and, upon being urged outwardly beyond the distal end of the catheter, they reassume their uncollapsed shape.
Nevertheless, performance of such filtration and protection devices is less than perfect. One significant drawback is the general lack of rigidity of the device. While shape-memory materials are used and the device, once released from the catheter, tends to assume an intended uncollapsed configuration, the path of the vessel within which it is intended to be installed can be tortuous. The guidewire upon which the device is installed, therefore, tends to alternately engage opposite sides of the internal vessel wall as the vessel sinuates back and forth. This circumstance can cause the filtration/protection device to become at least partially collapsed between the guidewire and the internal vessel wall. This can result in at least a portion of the mouth of the device being closed and not fully covering the cross-section of the vessel. At least a portion of flow through the vessel can, then, bypass the device.
At least one other circumstance might result in the filtration/protection device becoming at least partially collapsed and a commensurate closure of at least a portion of the mouth of the device. When the guidewire carries a percutaneous transluminal coronary angioplasty (PTCA) balloon, stent or IVUS catheter, the radial position of the guidewire within the internal vessel can be altered from a desired generally central location. When the guidewire is displaced in this manner, the device can become partially collapsed, as discussed above, with commensurate partial or complete closure of the mouth of the device. Again, at least a portion of flow through the vessel can, thereby, bypass the device.
It is to these problems and dictates of the prior art that the present invention is directed. It is an improved distal protection device deployable in a blood vessel which facilitates maximization of desired filtration/protection.